Structure−Function Relationships of Alternative Nitrogenases

Eady, Robert R.

doi:10.1021/cr950057h

Cited by 802 publications

(843 citation statements)

References 101 publications

Supporting

Mentioning

818

Contrasting

Unclassified

Order By: Relevance

“…Thus, compounds with two identical monodentate ligands such as 2 , appear to have structures that differ from tetrahedral only by virtue of the chelating ligand (Scheme 2b). In contrast, in some four-coordinate adducts such as L tBu FeH (4-tBu-py), L Me FeF(4-tBu-py) and L Me FeCl(tBupy) (3), the iron center deviates substantially from a tetrahedral geometry.…”

Section: Synthesis Of Four-coordinate Iron(ii) Diketiminate Complexesmentioning

confidence: 99%

Quantitative Geometric Descriptions of the Belt Iron Atoms of the Iron−Molybdenum Cofactor of Nitrogenase and Synthetic Iron(II) Model Complexes

et al. 2006

View full text Add to dashboard Cite

Six of the seven iron atoms in the iron-molybdenum cofactor of nitrogenase display an unusual geometry, which is distorted from the tetrahedral geometry that is most common in iron-sulfur clusters. This distortion pulls the iron along one C 3 axis of the tetrahedron toward a trigonal pyramid. The trigonal pyramidal coordination geometry is rare in four-coordinate transition metal complexes. In order to document this geometry in a systematic fashion in iron(II) chemistry, we have synthesized a range of four-coordinate iron(II) complexes that vary from tetrahedral to trigonal pyramidal. Continuous shape measures are used for a quantitative comparison of the stereochemistry of the Fe atoms in the iron-molybdenum cofactor with those of the presently and previously reported model complexes, as well as with those in polynuclear iron-sulfur compounds. This understanding of the iron coordination geometry is expected to assist in the design of synthetic models for intermediates in the nitrogenase catalytic cycle.

show abstract

Section: Synthesis Of Four-coordinate Iron(ii) Diketiminate Complexesmentioning

confidence: 99%

Quantitative Geometric Descriptions of the Belt Iron Atoms of the Iron−Molybdenum Cofactor of Nitrogenase and Synthetic Iron(II) Model Complexes

et al. 2006

View full text Add to dashboard Cite

show abstract

“…Using the presence of nifH mRNA as an indicator of nifH gene expression and diazotrophic activity, Noda et al (1999) demonstrated that the most highly expressed nitrogenases in the dry-wood termite Neotermes koshunensis (Kalotermitidae) were so-called alternative nitrogenases (anf) in Cluster II, paralogs of classical nitrogenases (nif) that contain neither molybdenum nor vanadium cofactors (Eady, 1996;Sicking et al, 2005). Closely related anfH genes are present also in Cryptotermes domesticus and Glyptotermes fuscus Yamada et al, 2007), but the general pattern of anfH expression in Kalotermitidae and the identity of the bacterium carrying these genes remain unknown.…”

Section: Introductionmentioning

confidence: 99%

Bacteroidales ectosymbionts of gut flagellates shape the nitrogen-fixing community in dry-wood termites

Desai

Brune

2011

The ISME Journal

View full text Add to dashboard Cite

Although it is well documented that the lack of nitrogen in the diet of wood-feeding termites is compensated by the nitrogen-fixing capacity of their gut microbiota, the bacteria responsible for this activity are largely unknown. Here, we analyzed the diversity and expression of nitrogenase genes (homologs of nifH) in four species of dry-wood termites (Kalotermitidae), which thrive on a particularly nitrogen-poor resource. Although each species harbored a highly diverse suite of termite-specific homologs in their microliter-sized hindgut, only a core set related to nifH genes of Treponema and Azoarcus spp., 'Azobacteroides pseudotrichonymphae', the first member of the Bacteroidales identified as a diazotroph, and termite-gut-specific anfH genes of hitherto unknown origin were preferentially expressed. Transcription patterns corroborated that the populations of active diazotrophs differ fundamentally between termite genera. Capillary-picked suspensions of the flagellates Devescovina arta and Snyderella tabogae revealed that their bacterial ectosymbionts each possess two paralogs of nifH, which apparently have been acquired consecutively during evolution of Bacteroidales, but only one of them (anfH) is actively expressed. Transcription patterns correlated neither with the molybdenum content of the diet nor with intestinal hydrogen concentrations, measured with microsensors. We propose that the nitrogen-fixing community in different dry-wood termites is shaped by the symbionts of their specific flagellate populations. Our findings suggest that the diazotrophic nature of 'Armantifilum devescovinae' has an important role in the nitrogen metabolism of dry-wood termites and is the driving force of co-evolution with its flagellate host.

show abstract

“…This cluster both binds the substrate N 2 and catalyzes the chemically difficult reduction of the N 2 triple bond to form NH 3 1. The V-Nitrogenases and Fe-Nitrogenases contain similar cofactors where the Mo is thought to be substituted by V or Fe, forming FeV-co and FeFe-co respectively 2 .…”

Section: Introductionmentioning

confidence: 99%

Extended X-ray Absorption Fine Structure and Nuclear Resonance Vibrational Spectroscopy Reveal that NifB-co, a FeMo-co Precursor, Comprises a 6Fe Core with an Interstitial Light Atom

et al. 2008

View full text Add to dashboard Cite

NifB-co, a Fe-S cluster produced by the enzyme NifB, is an intermediate on the biosynthetic pathway for the iron molybdenum cofactor (FeMo-co) of nitrogenase. We have used Fe K-edge extended xray absorption fine structure (EXAFS) spectroscopy together with 57 Fe nuclear resonance vibrational spectroscopy (NRVS) to probe the structure of NifB-co while bound to the NifX protein from Azotobacter vinelandii. EXAFS analysis of the NifX:NifB-co complex yields Fe-S distances of 2.26 Å and Fe-Fe distances of 2.66 Å and 3.74 Å. Search profile analyses reveals the presence of a single Fe-N (or C, O) interaction at 2.04 Å, implying that the interstitial light atom proposed to be present in FeMo-co is already inserted into NifB-co. NRVS reveals strong bands from Fe-S bending and stretching modes peaking around 270, 315, 385, and 408 cm −1 . Additional intensity at ~185 -200 cm −1 is interpreted as a set of cluster 'breathing' modes similar to those seen for the FeMo-cofactor. The strength and location of these modes also strongly suggest that the FeMo-co interstitial light atom seen in the crystal structure is already in place in NifB-co. Both the EXAFS and NRVS data are best simulated using a Fe 6 S 9 X trigonal prism structure analogous to the 6Fe core of FeMo-co, although a 7Fe structure made by capping one trigonal 3S terminus with Fe cannot be ruled out. This implies that the interstitial light atom is already present at an early stage in FeMo-co biosynthesis prior to the incorporation of Mo and R-homocitrate.

show abstract

Structure−Function Relationships of Alternative Nitrogenases

Cited by 802 publications

References 101 publications

Quantitative Geometric Descriptions of the Belt Iron Atoms of the Iron−Molybdenum Cofactor of Nitrogenase and Synthetic Iron(II) Model Complexes

Quantitative Geometric Descriptions of the Belt Iron Atoms of the Iron−Molybdenum Cofactor of Nitrogenase and Synthetic Iron(II) Model Complexes

Bacteroidales ectosymbionts of gut flagellates shape the nitrogen-fixing community in dry-wood termites

Extended X-ray Absorption Fine Structure and Nuclear Resonance Vibrational Spectroscopy Reveal that NifB-co, a FeMo-co Precursor, Comprises a 6Fe Core with an Interstitial Light Atom

Contact Info

Product

Resources

About